Since the first railway in the world is constructed by Britain in 1825, the problem of impact between wheels and steel rails and also rail gaps and the problem of thermal stress of steel rails have not been solved simultaneously and completely all the time.
For standard steel railways, transversal rail gaps have been reserved between steel rails to solve the problem of thermal stress of steel rails, which yet bring about the problem of impact between wheels and rails. Impact between wheels and rails not only significantly accelerates loss of wheels and rails, but also generates impact vibrations and noise. This not only significantly increases the cost of repair and replacement of trains and railways, but also reduces passenger comfort and cargo transportation safety.
For seamless steel railways, in order to solve the problem of impact between wheels and rails, standard steel rails are welded to form a seamless steel railway with a length of a few hundred meters to several kilometers, or a super long seamless steel railway is used. In this way, although impact between wheels and rails can be eliminated for the seamless steel rail, but transversal rail gaps still exist between the seamless steel rails. Therefore, by using seamless steel railway, the impact between wheels and rails can only be reduced rather than completely eliminated.
Seamless steel railways mainly use the design of thermal stress seamless line to limit thermal stress of the steel rails, that is, high-strength bolts, buckle fasteners or snap fasteners, etc. are used to lock the steel rails, so that free expansion and contraction of the seamless steel rails are limited via line resistance; alternatively, the type of thermal-stress-releasing seamless line design is used to reduce and control thermal stress of the steel rails. However, both methods can only limit and control thermal stress of the steel rail in a certain range, and if problem occur in some link of the thermal stress limitation and control (e.g., during locking of the steel rails), or if the ambient temperature changes beyond the design range (e.g., extreme weather occurs), accidents of breaking welds or expanding rails of the steel rails would occur. In case of seamless steel railways, welding and locking of steel rails are required, the qualities of rail welds, rail fasteners, sleepers, and roadbeds have greater impact on railway safety, and there are more uncertainties and higher probability of failure. Seamless steel rails are longer and thermal stress is greater, more attachments are needed for each steel rail, and there are more uncertainties and higher probability of failure. In areas having great temperature differences, thermal stress of the steel rails varies more, rail welds, rail fasteners, sleepers and roadbeds experience higher stress intensity, and there are more uncertainties and higher probability of failure. Seamless steel railways impose higher requirements on line stability, and geological, climate, and natural disasters have greater impact on railway safety. In addition, problems of unstable weld quality and high end breakage rates further exist in use of seamless steel railways. Therefore, seamless steel railway has not completely solved the problem of thermal stress on the steel rails, and there are still many safety risks.
Seamless steel railways require welding and locking of steel rails, which significantly add quality requirements and construction difficulties of rail welds, rail fasteners, sleepers and roadbeds, thereby multiplying construction and maintenance costs of railways. Seamless steel rails are longer, need on-site welding, requires large paving equipment and work in cooperation of more technical personnel, which increase costs of the equipment and labor for railway construction. Seamless steel rails are longer, which also increases production and transportation costs of steel rails. Further, repair and maintenance both are more difficult and demanding for seamless line, and this also significantly increase costs of repair and maintenance. Therefore, construction and maintenance costs of seamless steel railways are high.
In summary, standard steel railways solve the problem of thermal stress on the steel rails and yet bring the problem of impact between wheels and rails. Seamless steel railways cannot completely eliminate the impact between wheels and rails on one hand, and also multiply construction and maintenance costs of railways on the other hand. They cannot solve the problem of thermal stress of the steel rails completely, and there are many hidden safety hazards. Neither the standard steel railways rail nor the seamless steel railway can completely solve the problem of impact between wheels and rails and the problem of thermal stress of steel rails simultaneously.